Friday, March 1, 2013

What is love?

A psychoneuroendocrinological perspective on love

Leanne Fogg

What is love? I mean deep, passionate, head-over-heels love? Can’t-image-life-without-them
love? What about love that never fades? Emotions are not so easily defined or
measured, so the most honest answer I can provide lies within the endocrine
system: hormones don’t lie.

The Endocrine System

The endocrine system includes a series of glands that
release hormones (chemical messengers) into the bloodstream to elicit a
response. Hormones will bind to a receptor, eventually resulting in the
production of new proteins or an alteration in the activity of an existing
protein. Responses can be transient or long lasting, depending on structure and
composition of the hormone initiating the response. Testosterone and cortisol
are some commonly known hormones that are associated with feelings of love.
Other endocrine factors play roles in the emotion of love, including vasopressin,
oxytocin, dopamine, serotonin, and nerve growth factor.

Scientists recognize
three different stages of love: falling in love, passionate love, and companionate
love. Many would agree stages were assigned appropriately, but it is difficult
to umbrella the complexities of relationships into three categories – a prime
example of reductionism (taking something complex and breaking it down into
parts). When faced with the intricacies of love, a reductionist view can be a
good place to start.

Phase 1: Falling in
love

The first stage of a relationship is often very passionate,
intimate, and euphoric. Partners are generally excited, experiencing feelings
of infatuation and adoration toward their new mate. Although individuals
experience a lot of happiness in a new relationship, high cortisol levels
indicate feelings of stress during this phase. People who claim to have fallen
in love within the last 6 months had significantly higher cortisol levels than
individuals not in a relationship. Stress can result from feeling insecure,
fearing judgment and/or rejection. Both men and women possess great desire to
impress their mate, often resulting in mood and personality changes.

Although cortisol levels are high in both genders during
early love, hormonal cues are often distinct between men and women. Testosterone,
known for its primary role in the development of the male reproductive system,
is often elevated in males rather than in females. The male testes and female
ovaries secrete testosterone, influencing behavioral aspects of social
interactions, including aggression and sexual intimacy. Testosterone levels in young
lovers are often low in men and high in women when compared to their respective
controls (individuals currently not in a relationship). While the role of
testosterone is generally linked to reproductive efforts, the discrepancy of
testosterone levels between genders during early love remains unexplained.

Table 1: Hormonal changes in the early stages of love (Marazzitia, 2004)

It is believed that the elevated testosterone production in
single males is a product of mating effort – the increased time and energy
invested in obtaining a mate. This hormonal change could possibly be a product
of the “Coolidge effect” – thefluctuation of male libido given various mate choices. Increased
libido is observed when males are provided multiple females to mate with, while
decreased male libido results when only given one female mate. When males
“settle down” into a relationship, less energy is spent on finding a mate,
resulting in decreased testosterone levels. Alternatively, males in a relationship
who continue to pursue females other than their primary partner have higher
levels of testosterone than loyally committed males. Also, elderly men who
report high numbers of lifetime sex partners have elevated testosterone levels
compared to those with less sexual encounters.

The differences in testosterone levels between genders as
well as the elevated cortisol fade within 1-2 years after experiencing initial feelings
of love. Eventually, testosterone levels of both male and females will decrease,
and drop further throughout the progression of a relationship.

After the initial “honeymoon phase” of a relationship,
feelings of security, peace, and balance take over. Partners experience
“passionate love,” full of intimacy and satisfaction. As individuals become
more comfortable and self-confident, decreased cortisol levels can lead to
improved health benefits. These include reduced anxiety and depression as well
as improved immune defense, general health, and well-being. Increased
commitment and intimacy between partners often results in the formation of
strong pair bonds. Oxytocin and vasopressin are nanopeptides hormones (made of
nine amino acids) that facilitate the learning of personal recognition through
binding receptors (mainly) in the brain. Although they play a role in forming
early love connections, they continue to contribute to the strengthening of a
relationship. This peptidergic signaling coincides with dopaminergic reward
systems pathways, reinforcing the pair bond relationship.

Some relationships
can progress to a third state of “companionate love,” commonly referred to as
an “empty love.” This can be a result from dwindled passion, causing commitment
to be the crux of the relationship. Oxytocin and vasopression continue to
promote positive, comforting feelings of the pair bond, but diminishing
testosterone levels might elucidate feelings of a dull relationship. Breakups
can result at this stage, unless commitment is strong enough. The “4 year itch”
phenomenon is characteristic of couples not content with companionate love,
often resulting in a divorce 4 years into marriage. However, some couples claim
to share passionate love even after 20 years of marriage, suggesting that some
relationships remain in the early stages of love.

Long Distance

Long distance relationships can be an emotional
rollercoaster, influenced by changes in hormonal signaling initiated by the
physical presence of a pair bond partner. Women tend to have higher levels of
testosterone when their partner lives in the same city – possibly a result of
consistent reproductive effort. When partners are reunited after periods of
separation, testosterone levels spike, cortisol decreases, and sleep patterns are
altered. The difficult whirlwind of a long distance relationship is plagued
with hormonal fluctuations, often creating difficulties in maintaining a
partnership.

The complex sentiment of love is not so easily defined or
generally described. Most psychoneuroendocrinological studies on love have
focused on heterosexual interactions, describing the hormonal changes between males
and females in various situations. Love can be shared between any individuals –
the chemical makeup of love is not limited to the interworking of a
heterosexual relationship.

Peace, Love, and Hormones.

References:

Caldwell Hooper, A.E., S.W. Gangestad, M.E. Thompson, A.D. Bryan. 2011. Testosterone and romance: the association of testosterone with relationship commitment and satisfaction in heterosexual men and women. American Journal of Human Biology 23:553-555.

De Boer, A., E.M. Van Buel, G.J. Ter Horst. 2012. Love is more than just a kiss: a neurobiological perspective on love and affection. Neuroscience 201: 114-124.

Debiec, J. 2007. From affiliative behaviors to romantic feelings: a role of nanopeptides. FEBS Letters 581:2580-2586.

Diamond, L.M., A.M. Hicks, K.D. Otter-Henderson. 2008. Every time you go away: changes in affect, behavior, and physiology associated with travel-related separations from romantic partners. Journal of Personality and Social Psychology. 95(2):385-403.

Pollet T.V., L. van der Meij, K.D. Cobey, A.P. Buunk. 2011. Testosterone levels and their associations with lifetime number of opposite sex partners and remarriage in a large sample of American elderly men and women. Hormones and Behavior 60:72-77.